Meconium – What Is It? Everything You Need To Know

Meconium - What Is It? Everything You Need To Know

A few days after birth, babies pass their first bowel movement which is called meconium.

This sticky, tar-like substance is green-black in colour, and is simply waste produced in your baby’s intestine during pregnancy.

Sometimes babies pass meconium before or during labour. If the mother’s waters break and meconium is noticed, it can cause care providers to become concerned about the baby’s wellbeing.

Meconium may pass shortly after birth, even if baby has yet to feed. For many babies though, it will pass after they begin breastfeeding. The nutrient dense colostrum has a laxative effect and helps baby to pass the first few sticky bowel movements.

What Is Meconium?

Babies regularly swallow amniotic fluid from around 14 weeks of pregnancy. The amniotic fluid is important for fetal development, containing mucus, baby’s hair (lanugo), intestinal cells, bile and water.

The fluid passes through to the baby’s small intestine, which removes and absorbs the water. Any debris left behind is passed to the large bowel. This begins to build up, forming a sludgy tar-like substance called meconium. By the time the baby is full term, the meconium has filled most of the intestine.

In the first days after birth, your breasts produce colostrum. This substance has many positive benefits and has a natural laxative effect, helping to move the meconium from your baby’s bowel. Usually this happens within the first 12 hours following birth of a full term baby. If meconium hasn’t been passed within 48 hours of birth, caregivers may suspect intestinal obstruction.

Meconium Before Birth

If a baby passes meconium before birth, the amniotic fluid is stained and appears greenish in colour. The baby will also become covered in meconium, especially if there is a lot of vernix (waxy coating on skin). The baby may also swallow (not to be confused with aspirate) the meconium, which will not do any harm.

Babies who pass meconium before birth can do so because their digestive system has matured. They’re more likely to pass meconium before birth the longer they go past their due dates.

It can also be caused by a sudden and short compression of the cord or head. The momentary lack of oxygen can cause the sphincter muscles to relax, allowing the meconium to be pushed out. Often the heads of babies are quite compressed in the final moments of birth and some are found to have a trail of meconium when their bodies are born.

Meconium stained waters occurs in about 20% of full term births.

Is Meconium Dangerous?

If a woman’s waters break and meconium staining is noticed, it can cause a great deal of concern. If the colour of the water is greenish, usually this is an indication the meconium has only recently been passed. A brownish, yellow colour would indicate the meconium was passed some time earlier and is old.

The main concern with meconium stained fluid is the possibility of the baby having meconium on the lungs. This is known as meconium aspiration syndrome (MAS).

What Is Meconium Aspiration Syndrome?

During pregnancy, babies’ lungs are filled with amniotic fluid and if there is meconium it can get into the airways. During labour, if a baby is severely distressed and lacks oxygen for long enough, it’s possible for the baby to gasp and inhale any meconium present.

When inhaled, it can partially or completely block the baby’s airways, making breathing very difficult and reducing the amount of oxygen the baby receives. MAS can also cause a chemical irritation of the airways increasing breathing difficulty. Infection of the lungs is possible, as is inactivation of surfactant by the meconium. Surfactant is a substance that helps the lungs expand properly.

Of 20% of babies with meconium stained waters, around 2-5% will go on to develop MAS.

Signs of MAS include:

  • Rapid breathing (tachypnea)
  • Laboured breathing or grunting
  • Suspended breathing (apnea)
  • Low APGAR scores (colour, muscle tone, reflexes)
  • Cyanosis (blue colour on skin)
  • Over distended chest.

What Is The Treatment For Meconium Aspiration?

Current guidelines from the American Academy of Pediatrics state babies who have inhaled meconium should no longer be suctioned intrapartum (during birth). Previous practice would be to suction the baby once the head was born. This is longer standard practice.

If a baby has inhaled meconium and is active, appears well and has a good heart rate (above 100 beats per minute), care providers should monitor for signs of MAS that may appear in the first 24 hours.

Babies who have inhaled meconium and are not active, have low heart rates (under 100 beats per minute), limp with poor muscle tone, are likely to need immediate suctioning. Care providers will aim to clear the baby’s airway as much as possible to limit how much meconium is inhaled. A tube is inserted into the baby’s windpipe through the mouth or nose.

Babies with MAS are likely to spend time in the neonatal intensive care unit or special care nursery. They will be monitored for signs of infection, have frequent blood tests and may need oxygen treatment. Some babies with severe MAS may develop pneumonia. Most babies with severe MAS will experience wheezing and lung infections in the first 12 months of life but this should improve as their lungs develop new air sacs.

How Can I Avoid MAS?

The most obvious way to avoid a stressed baby is to have a calm and supportive birth environment and birth support. If a woman is disturbed and stressed during labour, this can have cause contractions to slow or stall. This can lead to the cascade of interventions to hurry it along, which further contributes to fetal distress. Read our 8 tips to help slow or stalled labours.

Interventions such as artificial rupture of membranes (breaking the waters), constant fetal monitoring, and induction or augmentation with artificial oxytocin can all cause your baby to become distressed. If your waters break and meconium is present, this will usually lead to monitoring, which reduces your ability to move.

If the meconium is thin and your care provider has determined your baby’s heart rate is fine, choose an upright birth position which allows the contractions to push fluid from the baby’s lungs and down out of the mouth and nose. Allowing the cord to continue pulsating to provide oxygen to your baby while transitioning to breathing air into the lungs.

It’s important to remember that meconium staining can occur in the absence of fetal distress and not all babies who become stressed pass meconium. It’s very rarely a problem and care providers can help prevent this event from happening by avoiding the use of interventions which increase the likelihood of fetal distress.

Most babies who pass meconium before the birth are post dates (beyond their estimated due date) and it’s simply a sign of a functioning digestive system. It’s no longer recommended to suction babies at birth but to monitor as necessary. Parents should be aware of the signs of MAS and seek professional attention if they become concerned about their baby’s breathing.

Recommended Reading: 42 Weeks Pregnant | Your Body and Your Baby.

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Sam McCulloch enjoyed talking so much about birth she decided to become a birth educator and doula, supporting parents in making informed choices about their birth experience. In her spare time she writes novels. She is mother to three beautiful little humans.

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